Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

224 Educability and Group Differences
educational attainment in Negroes. There was also a correlation
between spouses in skin color, showing that this characteristic is
a factor in assortative mating in the Negro population. Obviously,
to establish any direct correlation between intelligence and degree
of Caucasian admixture in Negroes would require the use of
non-visible genetic characteristics, which are therefore not a basis
for assortative mating or social discrimination, as an index of
Caucasian admixture.
GENETIC BIOCHEMICAL POLYMORPHISMS AND IQ
The use of genetic polymorphisms in the blood for researching this
problem was suggested independently by Shockley (1966), a
physicist noted for the invention of the transistor, and by Heston,
a psychiatric geneticist noted for his research on the genetics of
schizophrenia (e.g., Heston, 1966). Essentially, Heston has proposed
obtaining correlations between skin color (measured with a reflectance
spectrophotometer on the underside of the upper arm) and
mental test scores, on the one hand, and between percentage of
Caucasian admixture (based on a dozen or more blood groups)
and intelligence scores, on the other, and then testing the hypothesis
that the non-visible index of Caucasian admixture (blood
groups) correlates more highly with intelligence than the visible
index of skin color. If the blood groups measure of M (proportion
of Caucasian genes) correlates more highly with, say, IQ than does
skin color, the hypothesis of a racial genetic difference in intelligence
would be supported. Blood groups are a more reliable basis than
skin color for estimating Caucasian admixture because more genes
are involved and because blood groups, being non-visible, do not
enter into mate selection.
Heston, with quantitative geneticist Oscar Kempthorne and
statistician James Hickman, worked out a method for statistically
estimating the proportion of Caucasian genes in individual Negroes,
which is a more complex problem than the estimation of M, the
proportion of Caucasian genes in a particular hybrid Negro
population. The method for estimating the Caucasian admixture
of individual Negroes is as follows:
We have two ancestral racial groups, Caucasian (C) and
African (A). Also, we have some measurable genetic polymorphism,
G, which has 1, 2, 3 ... k forms. (A polymorphism is 2 or more